Click anywhere in the window. If you can’t see the window you’re looking for, drag other windows out of the way or click the yellow minimize button (-) in the top-left corner of a window to put it in the Dock.

Control-click an app icon in the Dock, and then choose an open window in that app from the menu that appears.

Press and hold an app icon in the Dock to see all open windows for that app, and then click the window you want to make active.
In many apps, including the Finder, choose Window >
“Bring All to Front.”

When a window is active, the buttons in the top-left corner are colored or more visible. You can use these buttons even if a window isn’t active. Some windows, such as the Fonts window, always appear in front of other windows.